Unloading valve for a hydraulic power unit or the like



June 20, 1961 F. E. NORLIN 2,989,066

UNLOADING VALVE FOR A HYDRAULIC POWER UNIT OR THE LIKE Filed Sept. 10, 1958 f 721/671257" Francis 1: fyflz'n 2,989,066 UNLOADING VALVE FOR A HYDRAULIC POWER UNIT OR THE LIKE Francis E. Norlin, Chesterland, Ohio, assignor to Borg- Warner Corporation, Chicago, 111., a corporation of Illinois Filed Sept. 10, 1958, Ser. No. 760,228 7 Claims. (Cl. 137-108) This invention relates to hydraulic power units, and, in particular, to a combination valve utilized in combination with a hydraulic power unit comprising a plurality of pumping units each having pressure loadable bushings associated therewith, and a common inlet means and a common outlet means respectively leading to and from the pumping units, the combination valve being adapted to cause unloading of certain of the pumping units while maintaining the remainder of the pumping units in operation when a first predetermined pressure value ofthe fluid pressure discharged by the pumping units into the common outlet means has been attained and being adapted to maintain the pressure value of the pressure fluid in the common outlet means of the remainder of the pumping units below a second predetermined pressure value.

Heretofore, hydraulic power units have been constructed where each hydraulic power unit comprises a plurality of commonly driven pumping units mounted within a housing. Each pumping unit comprises a pair of meshing gears which receive hydraulic fluid from a common inlet formed in the housing and deliver the same under pressure to a common outlet. A pair of pressure loadable bushings are operatively associated with each pumping unit. Each pair of bushings is adapted to be axially moved into engagement with the side faces of the respective gears to form pumping seals therewith when pressure fluid is applied to rear motive surfaces of the bushings whereby the respective pumping unit is permitted to deliver fluid under pressure to the outlet means. However, when a pair of bushings is unloaded, i.e., when no pressure fluid is applied to the rear motive surfaces thereof, the respective pumping unit is prevented from delivering fluid under pressure to the outlet means. Suitable conduit means are utilized to fluidly interconnect the outlet means of the hydraulic power unit with a utilization device whereby the fluid pressure delivered by the hydraulic power unit drives the utilization device. At certain times, the utilization device may be operating under difierent loads than at other times, and, therefore, it is not desirable that all the pumping units be functioning to supply pressure fluid for each particular operating condition. Valve means have been designed to be incoporated in each hydraulic unit or in the hydraulic system utilizing the hydraulic unit. The valve means is adapted to be responsive to the pressure value of the pressure fluid in the outlet means, the valve means being etfective to cause unloading of certain of the individual pumping units when the pressure value within the common discharge has reached a predetermined value. The remainder of the pumping units continue operating and supply the entire pressure fluid for the utilization device. A separate relief valve is disposed either in the outlet means or in the conduit means and is set to prevent the pressure value of the pressure fluid conveyed to the utilization device by the remainder of the pumping units from exceeding a second predetermined pressure value. Such hydraulic power units are well known in the art, one of which is fully disclosed by the United States patent to Lauck, No. 2,505,191.

The present invention relates to a valve which not only functions to cause unloading of certain of the individual pumping units when the pressure value of the pressure nited States Patent Iii.

fluid within the outlet means exceeds a first predetermined value, but also acts as a relief valve to prevent the pressure value of the pressure fluid in the outlet means from exceeding a second predetermined value.

It is, therefore, an object of this invention to provide a combination valve for use with a hydraulic power unit having a plurality of pumping units and effective to not only render certain of the pumping units of the hydraulic unit inetfective while maintaining the remainder of the pumping units in operation when the pressure value of the pressure fluid in the outlet means thereof has reached a first predetermined pressure value, .but also to prevent the pressure value in the outlet means from exceeding a second predetermined pressure value.

Another object of this invention is to provide a combination valve that functions as an unloading valve and as a relief valve.

Other and more particular objects, advantages, and uses of this invention will become apparent from a reading of the following specification taken in connection with the accompanying drawings forming a part thereof and wherein the figure is a schematic drawing illustrating a hydraulic power unit and an enlarged cross-sectional view of the combination unloading and relief valve utilized therewith.

The particular details of the hydraulic power unit will not be described as such structure is common in the art and is fully disclosed in the aforementioned patent to Lauck, No. 2,505,191. It is merely suflicient to state that the gear pumping units of the hydraulic power unit have pressure loading or receiving chambers 47 and 4-8 formed respectively by rear motive surfaces of respective pairs of axially movable bushings. Pressure fluid is delivered respectively to the pressure receiving chambers 47 and 48 by the pumping units P-l and P-2 in a manner well known in the art, whereby the force of the pressure fluid acting against the rear motive surfaces of the respective bushings tends to axially move the bushings toward the respective gear side faces to provide pumping seals therewith. When pressure fluid is present in the chambers 47 and 48, the pumping units P-1 and P-2 are permitted to deliver fluid under pressure to the outlet means 15, and when no pressure fluid is present in the chambers 47 and 48, the pumping units P-1 and P-Z cannot deliver fluid under pressure, as there are no pumping seals for the pumping chambers and the fluid delivered by the pumping units P1 and P2 escapes back to the inlet means 14 between the axially movable bushings and the associated gear side faces.

As shown in the drawing, the inlet means 14 is adapted to convey fluid from a source (not shown) to the pumping units P-1 and P-2. respectively, the inlet of the pumping unit P-2 being interconnected with the inlet means 14. Outlets 56 and 57 of the pumping units P-l and P-2 respectively are interconnected with the outlet means 15, the outlet 57 of pumping unit P-2 being interconnected with the outlet means 15 by a passage means 58 formed in the housing section 10. A one-way valve 59 is disposed within the outlet means 15 intermediate the outlets 56 and 57 of the pumping units P-1 and P-2 and is normally biased by a spring 60 to a closed position preventing the flow of fluid from the outlet 56 through the outlet means 15. The one-way valve 59 is so constructed and arranged that pressure fluid discharged by the pumping unit P-1 is permitted to pass out through the outlet means 15 when the force of the fluid discharged thereby exceeds the force of the spring 60 permitting the valve 59 to open. However, if the pumping unit P-1 is not operating and the pumping unit P-2 is operating, the one-way valve 59 prevents fluid discharged by the pump ing um't P-2 from entering the outlet 56 of the pumping unit P-1 and thus tending to cause a reverse rotation thereof by causing the pumping unit P-1 to act as a motor.

As shown in the drawing, a valve unit, generally indicated by the reference letter V, is disposed within the housing section 10. The housing section is suitably bored to provide coaxial, interconnected bores 61, 62, 63, and 64-, each having a larger diameter than the preceding bore. The right end of the bore 63 is suitably internally threaded at 65 to cooperate with external threads 66 formed on a plug member 67 telescopically received Within the bores 63 and 64 of the housing section 10. The plug member 66 is provided with a bore 68 interrupting an end 69 thereof, which is adapted to abut an outwardly projecting flange portion 70 of a sleeve member 71 and maintain the sleeve member 71 within the bores 62 and 63, the flange portion 70 thereof engaging a shoulder 72 formed by the juncture of the bores 62 and 63. The sleeve member 71 is suitably bored to Provide coaxial interconnected bores 73, 74, and 75, each having a larger diameter than the preceding bore. A cylindrical member 76 is disposed within the bore 73 of the sleeve member 71 and engages a shoulder 77 formed at the juncture of the bores 73 and 74 at one end thereof and abuts a wall 78 of the housing section 10 at the other end thereof.

The sleeve member 71 is provided with an annular groove 79 in the outer periphery thereof and with a pair of spaced annular grooves 80 and 81 in the internal periphery thereof, the internal periphery being defined by the bore 75 formed therein. The annular groove 79 is fluidly interconnected with the annular groove 80 by a plurality of radial passages or ports 82 formed in the sleeve member 71. Similarly, the annular groove 79 is fluidly interconnected with the annular groove 81 by a plurality of angularly disposed passages or ports 83 formed in the sleeve member 71. The juncture of the bore 75 in the sleeve member 71 with the end of the flanged portion 70 thereof forms a fixed valve seat means 84 for a purpose hereinafter described.

A valve member or piston 85, having an enlarged cylindrical portion 86 at one end thereof and a spaced, interconnected, conical portion 87 at the other end thereof, is telescopically disposed within the valve unit V whereby the enlarged cylindrical portion 86 thereof is disposed within the bore 75 of the sleeve member 71 and the conically shaped portion 87 is disposed within the bore 68 of the plug member 67. The conical portion 87 of the valve member 85 is normally urged into sealing engagement against the fixed valve seat 84 by a compression spring 88 disposed within the bore 68 of the plug member 67, the spring 88 having one end 89 thereof in engagement with the valve member 85 and the other end 90 thereof in engagement with a movable piston member 91 telescopically disposed within the bore 68. The plug member 67 is formed with a centrally disposed, threaded aperture 92 which receives an adjusting screw 93. The adjusting screw 93 projects beyond the plug member 67 and engages the movable piston 91. By selectively adjusting the position of the adjusting screw 93 relative to the plug member 67, the movable piston 91 may be axially moved within the bore 68 to a new position whereby the compression force of the spring 88 may be adjusted to any predetermined force tending to maintain the conical portion 87 of the valve member in sealing engagement with the fixed valve seat 84.

A movable valve seat member 94, having an outwardly projecting flanged end portion 95, is telescopically disposed within a bore 96 passing centrally through the cylindrical member 76. A passage 97 is formed in the movable valve seat member 94, the passage 97 forming a conical valve seat 98 at the flanged portion 95 thereof against which an end 99 of the movable valve member 85 is adapted to sealably engage. A compression spring 100 is disposed between the end 78 of the housing section 10' and an abutment means 101 formed on the movable valve seat member 94. The compression force of the spring 100 tends to maintain the movable valve seat member 94 in engagement with the end 99 of the movable valve member throughout a predetermined axial movement of the valve member 85 to the right, as viewed in the drawings. Axial movement of the movable valve seat member 94 to the left is limited by the outwardly flanged portion thereof abutting an end 102 of the cylindrical member 76, and axial movement to the right thereof is limited by a shoulder 103 formed by the juncture of the bores 74 and 75 of the sleeve member 71.

The passage 97 formed in the movable valve seat member 94 is fluidly interconnected with the outlet means 15 of the hydraulic unit A by a passage means 104 formed in the housing section 10. The annular groove 79 formed in the sleeve member 71 is fluidly interconnected with the pressure loading chamber 47 of the pumping unit P-l by a passage means 105 formed in the housing section 10. The bore 68 formed within the plug member 67 is fluidly interconnected with the inlet means 14 by a plurality of radially disposed slots 106 formed in the plug member 67, an interconnected annular groove 107 formed in the housing 10, and a passage means 108 formed in the housing section 10, the passage means 108 being interconnected with the inlet means 14 at one end thereof and being interconnected with the annular groove 107 at the other end thereof.

The operation of the hydraulic power unit A will now be described. The outlet means 15 is fluidly interconnected with a hydraulic utilization device M, such as a hydraulic motor. It is to be understood that the compression force of the spring 88 is greater than the compression force of the spring 100. In this manner, the movable valve member 85 is urged to the left whereby the conical portion 87 thereof is in sealing engagement with the fixed valve seat 84 and the end 99 of the cylindrical portion 86 thereof is in sealing engagement with the movable valve seat 94. When both pumping units P-1 and P2 are receiving fluid from the inlet means 14 and discharging the fluid under pressure into the outlet means 15 to be conveyed to the motor M, the pressure value of the pressure fluid in the outlet means 15 is sensed by the valve unit V through the passage means 104 in the following manner. The force of the pressure fluid in the outlet means 15 is, in effect, acting against the end 99 of the movable valve member 85 tending to move the valve member 85 to the right in opposition to the compression force of the spring 88. As long as the compression force of the spring 88 is greater than the force of the pressure fluid in the outlet means 15, both pumping units P-1 and P-2 will be operating in a normal manner to supply pressure fluid to the motor M for driving the same. However, when the force of the pressure fluid in the outlet means 15 exceeds the compression force of the spring 88, e.g., when the load on the motor M increases, the valve member 85 will be urged to the right, as viewed in the drawings, thereby moving the conical portion 87 thereof away from the fixed valve seat 84 permitting the pressure fluid within the pressure loading chamber 47 of the pumping unit P1 to escape through the passage means 105, annular groove 79, passages 83, bore 68 of the plug member 67, slots 106, annular groove 107, and passage means 108, to the inlet means 14. The pumping unit P-l is now ineffective to deliver pressure fluid to the outlet means 15 because no pressure fluid is now present in the pressure loading chamber 47 to urge the bushings 24 and 25 into sealing engagement with respective gears 18 and 19 to provide the necessary pumping seals. The valve 59 is now moved to its closed position by the spring 60 preventing the pressure fluid discharged by the pumping unit P-2 from being delivered to the pumping unit P-l. Since the valve member 85 has moved slightly to the right to permit the unloading of the pumping unit P-l, the movable valve seat 94 by means of the compression spring 100 follows this axial movement of valve member 85 and remains in sealing engagement with the end 99 thereof. It is to be understood that only a slight axial movement of the valve member 85 to the right is necessary to permit the unloading of the pumping unit P-1 whereby the flanged portion 95 of the movable valve seat 94 is disposed between the stop means 102 and 103. Since the spring 88 is compressed by the slight movement of the valve member 8-5 to the right to permit the escape of fluid from the pressure loading chamber 47 of pumping unit P1, the force needed to urge the member 85 further to the right must be greater than the force initially required to axially move the valve member from engagement with the fixed valve seat 84.

The pumping unit P-Z now supplies the entire pressure fluid to the motor M through the outlet means 15.

If the load on the motor M increases still further, it can valve member 85 will axially move the valve member 85 further to the right. When the valve member 85 has been moved a suificient distance to the right, the movable valve seat 94 will engage the stop means or shoulder 103 and be prevented from following further axial movement of the valve member 85, whereby the end 99 of the valve member 85 will move out of engagement from the movable valve seat 94, permitting pressure fluid from the outlet means 15 to be conveyed to the inlet means 14 by means of passage means 104, passage means 97, annular groove 80, ports 82, annular groove 79, ports 83, bore 68, slots 106, annular groove 107, and passage means 108. In this manner, the pressure value of the pressure fluid within the outlet means 15 is prevented from exceeding a second predetermined value.

Subsequently, when the pressure value of the pressure fluid within the outlet means 15 drops below this second predetermined value, the force of the compression spring 88 will move the valve member 85 to the left whereby the end 99 thereof will again engage the movable valve seat 94 and prevent further escape of pressure fluid from the outlet means 15 to the inlet means 14. When the pressure value of the pressure fluid within the outlet means 15 drops below the first predetermined value, the force of the compression spring 88 is suflicient to cause further movement of the valve member 85 to the left, whereby the conical portion 87 thereof engages the fixed valve seat 84 and prevents further escape of pressure fluid from the pressure loading chamber 47 of the pumping unit P-1 to the inlet means 14 in order that the pumping unit P-1 can again be pressure loaded and deliver pressure fluid to the outlet means 15. By thus providing the valve unit V in combination with the hydraulic unit A, it can be seen that damage due to excessive pressure values in the hydraulic system is prevented by means of the unloading feature and relief valve feature of the combination valve unit V sensing, in effect, the loads imposed upon the motor M or other utilization devices and preventing any resulting excessive pressures.

Therefore, it can be seen that the combination valve unit V not only provides for unloading the pumping unit P-l when the pressure value of the pressure fluid within the outlet means 15 exceeds a first predetermined pressure value, but also acts as a relief valve permitting the escape of. pressure fluid from the outlet means 15 when the pressure value therein exceeds a second predetermined force.

While the combination valve unit V has been described as being disposed within a hydraulic power unit, it is to be understood that the combination valve unit V could be a separate structure and utilized in combination with other types of hydraulic systems.

While this invention has been disclosed in connection with one specific embodiment thereof-it is to be understood that this was'by way of example rather than limitation, and it is intended that the invention be defined by the appended claims.

What is claimed is:

' 1. An unloading valve unit comprising: a housing having a bore therein; said housing being further provided with pressure and unloading inlets and a common outlet all communicating with said bore; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed thereon; fixed valve seat means disposed in said bore; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said valve surface means is in engagement with said fixed valve seat means to prevent fluid communication between said unloading inlet and said outlet; movable valve seat means disposed in said bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; means for maintaining said movable valve seatmeans in engagement with the other of said valve surface means throughout a predetermined portion of the axial movement of said valve member from its predetermined position in response to excessive fluid pressure in said pressure inlet and said outlet; and means for arresting movement of said movable valve seat means after the predetermined portion of the axial movement of said valve member so that further movement of the valve member separates saidvalve memberfrom said movable valve seat means-whereby a greater fluid force is required to axially move'said valve member in opposition tosaid biasing means in order to disengage said other valve surface means from said movable valve seat means than the fluid force required to disengage said one valve surface means'from said fixed valve seat.

2. An unloading valve unit comprising: a housing having a bore therein; said housing being further provided with pressure and unloading inlets and a common outlet all communicating with said bore; an axially movable valve plunger disposed in said bore, said valve plunger having a pair of spaced valve surface means formed thereon; fixed valve seat means disposed in said bore; means defining a bore in said fixed valve seat means; biasing means tending to maintain said valve plunger in apredetermined position relative to said housing whereby one of said valve surface means is in engagement with said fixed valve seat means to prevent fluid communication between said unloading inlet and said outlet; movable valve seat means disposed in said fixed valve heat bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; means for maintaining said movable valve seat means in engagement with the other of said valve surface means throughout a predetermined portion of the axial movement of said valve plunger from its predetermined position in response to excessive fluid pressure in said pressure inlet to prevent fluid communciation between said pressure inlet and said outlet; and means for arrestingmovement of said movable valve seat means after the predetermined portion of the axial movement of said valve member so that further movement of the valve member separates said valve member from said movable valve seat means whereby a greater fluid force is required to axially move said valve plunger in opposition to said biasing means in order to disengage said other valve surface means from said movable valve seat means than the fluid force required to disengage said one valve surface means from said fixed valve seat.

3. An unloading valve unit comprising: a housing having a bore therein; said housing being further provided with pressure and unloading inlets and a common outlet all communicating with said bore; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed thereon; fixed valve-seat means disposed in said bore; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said valve surface means is in engagement with said fixed valve seat means to prevent fluid communication between said unloading inlet and said outlet; stop means in said bore; movable valve seat means disposed in said bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; and resilient means tending to maintain said movable valve seat means in engagement with the other of said valve surface means to prevent fluid communication between said pressure inlet and said outlet, said movable valve seat means engaging said stop means and being disengaged from said other valve surface means when said valve member is moved a predetermined distance from its predetermined position in response to excessive fluid pressure in said pressure inlet whereby a greater fluid force is required to axially move said valve member in opposition to said biasing means in order to disengage said other valve surface means from said movable valve seat means than the fluid force required to disengage said one valve surface means from said fixed valve seat.

4. An unloading valve unit comprising: a housing having a bore therein; said housing being further provided with pressure and unloading inlets and a common outlet all communicating with said bore; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed therein; fixed valve seat means disposed in said bore; means defining a bore in said fixed valve seat means; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said valve surface means is in engagement with said fixed valve seat means to prevent fluid communication between said unloading inlet and said outlet; stop means in said fixed valve seat bore; movable valve seat means disposed in said fixed valve seat bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; and resilient means tending to maintain said movable valve seat means in engagement with the other of said valve surface means to prevent fluid communication between said pressure inlet and said outlet, said movable valve seat means engaging said stop means and being disengaged from said other valve surface means when said valve member is moved a predetermined distance from its predetermined position in response to excessive fluid pressure in said pressure inlet whereby a greater fluid force is required to axially move said valve member in opposition to said biasing means in order to disengage said other valve surface means from said movable valve seat means than the fluid force required to disengage said one valve surface means from said fixed valve seat.

5. An unloading valve unit comprising: a housing having a bore therein; means defining a plurality of spaced passage means in said housing each being interconnected with said bore; said passage means comprising pressure and unloading inlets and a common outlet; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed thereon; fixed valve seat means disposed in said bore; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said surface means is in engagement with said fixed valve seat means thereby preventing communication between said unloading inlet and said outlet; movable valve seat means disposed in said bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; means for maintaining said movable valve seat means in engagement with the other of said valve surface means throughout a predetermined portion of the axial movement of said valve member from it predetermined position in response to excessive fluid pressure in said pressure inlet; and means for arresting movement of saidmovable valve seat means after the predetermined portion of the axial movement of said valve member so that further movement of the valve member separates said member from said movable valve seat means, said movable valve seat means preventing communication between said pressure inlet and said outlet when said movable valve seat means is in engagement with said other valve surface means whereby a greater fluid force is required to axially move said valve member in opposition to said biasing means in order to permit communication between said pressure inlet and said outlet than the fluid force required to permit communication between said unloading inlet and said outlet.

6. An unloading valve unit comprising: a housing having a bore therein; means defining a plurality of spaced passage means in said housing each being interconnected with said bore; said spaced passage means comprising pressure and unloading inlets and a common outlet; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed thereon; fixed valve seat means disposed in said bore; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said surface means is in engagement with said fixed valve seat means thereby preventing communication between said unloading inlet and said outlet; stop means in said bore; movable valve seat means disposed in said bore; said unloading inlet being disposed between said fixed valve seat means and said movable valve seat means; and resilient means tending to maintain said movable valve seat means in engagement with the other of said valve surface means, said movable valve seat means preventing communication between said pressure inlet and said outlet when said movable valve seat means is in engagement with said other valve surface means, said movable valve seat means engaging said stop means and thus being disengaged from said other valve surface means when said valve member is moved a predetermined distance from its predetermined position in response to excessive fluid pressure in said pressure inlet, whereby a greater fluid force is required to axially move said valve member in opposition to said biasing means in order to permit communication between said pressure inlet and said outlet than the fluid force required to permit communication between said unloading inlet and said outlet.

7. An unloading valve unit comprising: a housing having a bore therein; means defining first, second, and thirdspaced passage means in said housing each being interconnected with said bore; an axially movable valve member disposed in said bore, said valve member having a pair of valve surface means formed thereon; fixed valve seat means disposed in said bore, said fixed valve seat means being disposed between said first and second passage means; biasing means tending to maintain said valve member in a predetermined position relative to said housing whereby one of said surface means is in engagement with said fixed valve seat means thereby preventing communication between said first and second passage means; movable valve seat means disposed in said bore, said movable valve seat means being disposed between said second and third passage means; means for maintaining said movable valve seat means in engagement with the other of said valve surface means throughout a predetermined portion of the axial movement of said valve member from its predetermined position in response to excessive fluid pressure in said third passage means; and means for arresting movement of said movable valve seat means after the predetermined portion of the axial movement of said valve member so that further movement of the valve member separates said member from said movable valve seat means, said movable valve seat means preventing communication between said third passage means 10 I and either of said first and second passage means when required to permit communication between said first and said movable valve seat means is in engagement with second passage means. said other valve surface means whereby a greater fluid force is required to axially move said valve member in R f es Cit d in the file of this patent opposition to said biasing means in order to permit com- 5 munication between said third passage means and either UNITED STATES PATENTS of said first and second passage means than the fluid force 2,505,191 Lauck Apr. 25, 1950 

